Add CancelChannelCreation() in protocol::Session interface.

remoting/protocol/rtp_video_writer.h

Index: remoting/protocol/rtp_video_writer.h
diff --git a/remoting/protocol/rtp_video_writer.h b/remoting/protocol/rtp_video_writer.h
index 93d2a648def6da8333ab13e184eb7e3343c5b367..950d76e0cb8c6aabb58a7e0a30a77d64ac0c199a 100644
--- a/remoting/protocol/rtp_video_writer.h
+++ b/remoting/protocol/rtp_video_writer.h
@@ -24,7 +24,7 @@ class RtpVideoWriter : public VideoWriter {
   virtual ~RtpVideoWriter();
 
   // VideoWriter interface.
-  virtual void Init(protocol::Session* session,
+  virtual void Init(Session* session,
                     const InitializedCallback& callback) OVERRIDE;
   virtual void Close() OVERRIDE;
 
@@ -36,6 +36,8 @@ class RtpVideoWriter : public VideoWriter {
  private:
   void OnChannelReady(bool rtp, net::Socket* socket);
 
+  Session* session_;
+
   bool initialized_;
   InitializedCallback initialized_callback_;